[Fit The Body]: F4 shoulder bag adopts three-dimensional storage space design, which can adapt to your body in all directions. Rotatable self-adaptive pivot, designed to be worn both on the left and right side. (Note: As mask packs and tools have been discontinued, F4 doesn't include these accessories now.) [Humanized Design]: The sling bag not only features ergonomically designed quick-release buckle shoulder strap that opens and closes in one second but aslo uses an elastic cloth non-slip mechanism. The strap can be adjusted freely according to your tightness requirements to ensure comfort. [Multifunction Storage Layers]: Expandable space when needed :30mm/1.2in--50mm/2.0in, just unzip the side zipper. The front pocket is equipped with a detachable keychain, and the magnetic phone pocket is hidden on the back. Multiple compartments provide enough space for essentials. [Materials & Dimensions]: Size: 15.7*9.6*1.2in, weight is only 0.8lb.